When should I use the interface List<> instead of Collection<>

Question

My question is pretty much the oneliner that makes up the title. When is it appropriate to use the List interface instead of the Collection interface?

Is it just a question about clarity and readability, i.e. the intention of the code is clearer if I use either List or Collection depending on my code, or are there some other advantages that I'm unaware of?

Answer 1

One can argue either way, assuming, of course, that you're not dependent on the methods/features of List, and none of the other methods you'll be calling expect List.

There's the argument that it's best to use the most general type that suits the job, to allow code modification/reuse that might lead to switching to a non-List class.

There's also the argument that it's best to use the most specific type that encompasses all planned uses, to have the most power and flexibility within the domain of the planned uses. Using a more specific type also is a sort of self-documentation in that it indicates the narrowness of the code functionality.

In my experience the benefits of code reuse tend to be overstated, and rarely bear fruit outside of code bases that are developed for multiple use. So I'd tend to favor using the more specific type.

Answer 2

When you need the below benefits:

In addition to the operations inherited from Collection, the List interface includes operations for the following:

Listed as

Positional access — manipulates elements based on their numerical position in the list

Search — searches for a specified object in the list and returns its numerical position

Iteration — extends Iterator semantics to take advantage of the list's sequential nature

Range-view — performs arbitrary range operations on the list.